Hypertension (HTN) is a major risk factor for cardiovascular events. Its etiology is multifactorial and poorly understood. This application aims to elucidate the molecular mechanisms that link variants in 3 newly identified HTN susceptibility genes and is motivated by several lines of evidence: (1) Multiple linkage studies of HTN- related phenotypes suggest the presence of a blood pressure (BP) locus on human chromosome 1q23-q32;(2) BP-related QTLs have been mapped to the homologous region of human 1q23-q32 in mouse and rat;(3) In humans, polymorphisms in three HTN candidate genes that map to 1q23-q32, ATP1B1, RGS5, and SELE, have been associated with BP levels in multiple studies;and (4) The phenotypic effects of these genes appear to be cumulative, accounting for 2-4 mmHg BP difference individually and up to 10 mmHg when combined. All three genes encode proteins that have putative functions important in BP regulation. However, exactly how variants in these 3 genes perturb BP homeostasis, are not known. To address these issues, we will carry out a multifaceted analysis to identify and characterize potentially functional variants in these three genes. In Aim 1, we will characterize all common variants in RGS5 and SELE in effort to identify additional SNPs that may be more strongly associated with BP variation than those already known. In Aim 2, we will select the potentially functional SNPs identified from Aims 1 and 2, and test these for gene- environment interactions in an independent population of Old Order Amish, a unique closed founder population that is relatively homogeneous with respect to genetic background and lifestyle. Specifically, we will test for associations of these SNPs with BP responses to cold pressor stress and dietary salt interventions to gain insights into the mechanisms by which these genes may influence BP regulation. In Aim 3, we will perform functional testing of an hypothesized polymorphic functional U/GU-rich element in the 3'UTR of ATP1B1 by assessing the impact of the sequence variants on polyadenylation of the mRNA. Knowing the causative alleles of these 3 genes, and the pathways compromised by such alleles can lead to discovery of accurate and low-cost pre-symptomatic diagnosis and customized treatment for HTN. Given the high incidence of HTN and the high mortality and morbidity attributed to HTN, these advances will impact substantially on the quality of life of millions of people worldwide suffering from HTN-related complications.